Cachexia is a wasting syndrome characterized by physical wasting associated with loss of weight and muscle mass. These symptoms leave individuals affected by the syndrome extremely weak and unable to perform everyday tasks. Cachexia often is associated with diseases such as cancer, AIDS, and cardiovascular disease. According to the National Cancer Institute, almost one-third of cancer deaths may be caused by cachexia. Despite this remarkable statistic, there currently appear to be no effective treatments for cachexia.
A number of hormones that influence satiety, gastrointestinal motility, and blood glucose levels are secreted in the gastrointestinal tract. One of these hormones is ghrelin.
The peptide ghrelin was identified as the ligand of the growth-hormone secretagogue receptor type 1a (GHSR1a), and plays an important role in a number of biological systems, such as the release of growth hormone, the release of insulin, the stimulation of appetite, and gastric motility. Ghrelin is a 28 amino acid peptide hormone with its third residue (Ser3) modified with an octanoyl acid moiety. This latter modification appears to be important for ghrelin's interaction with GHSR1a, and, thus, its activity. Ghrelin is formed by the cleavage of preproghrelin, which produces at least two distinct peptides, ghrelin and obestatin.